Vitamin D is a steroid hormone best known for its activity in regulating calcium and bone metabolism. The active form of vitamin D is calcitriol [1,25-(OH)2D3]. Epidemiologic evidence suggests that calcitriol may play an important role in the development of colon and prostate cancer. Preclinical study of cancer cell lines have shown that calcitrol can kill tumor cells, however, animal studies have shown that the doses required also induce hypercalcemia. Prednisone is effective in reducing hypercalcemia. The premise of this study is to conduct a phase I;II study to evaluate the combined approach of calcitrol and prednisone in patients with advanced cancer.